1. Field of the Invention
The present invention relates to a method and a device for determining the delivery volume of an injection pump.
2. Description of Related Art
In principle, it is quite simple to determine the delivery volume of a pump within a test system. However, it is not desirable to uninstall it from the injection system and to insert it in a test system for the purpose of determining or checking the working capacity of an injection pump.
A current, no non-invasive methods or devices for determining the delivery volume of an injection pump installed in an injection system are offered on the market.
From published European patent application EP 1 226 355 B1, only a diagnosis method is known by which merely references to different errors or malfunctions of an injection pump can be determined without “invasive” intervention in the injection system. In this known method, the time characteristic of the pressure on the pressure side of the injection pump is detected essentially with the aid of a pressure sensor operating as component of the injection system for its control in the adaptation to different loading or operating states of the engine, and the time characteristic is subsequently converted into a frequency spectrum with the help of a computer, the frequency spectrum exhibiting clear maximums in the base or fundamental frequency of the pump, and also in its multiple, as a function of the engine speed in an intact injection pump. In the case of a three-piston pump provided according to published European patent application EP 1 226 355 B1, the maximums lie at the fundamental frequency f1 as well as twice or triple the fundamental frequency, i.e., at f2=2f1, and f2=3f1. By subsequently comparing the frequency spectrum of the pump to be checked with a standard frequency spectrum of a fault-free injection pump, it is possible to derive empirically verifiable references to different faults of the injection pump as a function of the individually determined differences. However, no information whatsoever about the actual delivery volume of the injection pump to be checked or its relative output capacity in comparison with a theoretical delivery volume are determined in this manner. Thus, the parameter that is decisive for the output capacity of an injection pump, i.e., the delivery volume or an equivalent parameter, is not determined.